The proposed standard also authorizes provincial level governments to increase or decrease the content by up to 30 percent, depending on local dietary requirements.

With the margin, the top level of iodine could reach 39mg/kg and the lowest 14mg/kg.

Details of the proposed change are available on the ministry's website, which is seeking public input on the issue until September 12.

"People in different regions consume different amounts of salt, so it's impractical to look for a unified standard of benefit to all," said Chen Zupei, a senior researcher at the Ministry of Health, who participated in drafting the new standard.

The ministry also said on Monday that although the current level of iodine is acceptable to the majority of the population, residents in five out of China's 34 provinces, autonomous regions and municipalities consume an excessive amount of iodine from table salt, while those in 16 other provinces consume more than is considered healthy.

Chen said the regions that consume an excessive amount of iodine are not in coastal areas where more seafood is readily available.

"People in Central China, such as Hunan province, usually take more salt than people in coastal areas, so their iodine levels are higher," Chen said.

According to the ministry, statistics from 2009 show that nearly 31 million people in the provinces of Shandong, Hebei, and Jiangsu had abnormal levels of iodine in their bodies.

Overconsumption of iodine may lead to thyroid problems. The latest available data on the subject from the China Medical Association indicated that there are 50 million people in China with thyroid problems.

This is the fourth time the Chinese government adjusted the iodine level in table salt since 1995.

The Ministry of Health on Monday also made public a draft regulation on the usage of edible flavors, which bans essence as an additive in 25 types of food, including rice, milk, fresh meat, sugar, salt, eggs and honey.

In regard to other products, in which the use of edible essence is permitted, the draft regulation requires producers to clearly label each of the additives, so that shoppers can choose whether to consume them.